The usual failure is a line or two not lighting at the bottom or the right edge of these displays, and is almost always caused by the connections at the glass, not on the board.

It's rare to have a line out in the middle of the dot matrix, but I've seen it happen.

These used to be fairly painless to replace, but now they cost $499.00. A lot more incentive to attempt to repair!

A line not lighting up at all is likely a broken connection, under the epoxy, where the conductive (almost ink-like) trace on the glass connects to the solder at the edge of the glass. I've fiddled with a bunch of these through the years, and with too-much-labor, you can more often than not make connection with a tiny bit of wire-wrap (30 gauge) wire after you expose the problem.

The problems I've gotten fixed have almost always been mechanically testable... you could press on the suspect junction at the glass and get it to work while applying pressure. Remove pressure and the line went dark again.

This could be electrical... the chip not sending the signal. Those kinds of problems always used to be 'buy another display', but for the past few years they became 'bitch as you buy a new display, and put the bad one in a box in case I can find someone to repair this later'. Hehe.

I'm hoping someone here on pinside knows of a technician who is making an effort to keep these displays running, but I don't know anybody who can help you.

My advice? If you can get the display line to come on with pressure at the connection of the glass, try to fix that connection. If you can verify that the chip isn't putting out a signal, and you can do surface mount repair work, replace the chip. (I've never done this, but it should be fairly straightforward.)

Good luck!